High dynamic range (HDR) imaging technologies have introduced a new era of recording and reproducing the real world with digital imaging. While traditional low dynamic range (LDR) images only contain device-referred pixels in a very limited color gamut, HDR images provide the real radiance values of natural scenes. HDR textures facilitate improvements in the lighting and post-processing of images, resulting in unprecedented reality in rendering digital images. Thus, supporting HDR textures has become the trend in designing both graphics hardware and application programming interfaces (APIs). However, LDR textures continue to be indispensable to efficiently support existing features of imaging technologies, such as decal maps, that do not typically require the expansive HDR resolution.
One of the challenges in using textures in imaging is that the size of textures is generally large. The LDR textures in typical 24 bit per pixel (bpp) raw red-green-blue (RGB) format typically consume too much storage and bandwidth. HDR textures, which are usually in half-floating or floating-point format in current rendering systems, can cost 2 to 4 times more space than the raw LDR textures. Large texture size constrains the number of HDR textures available for rendering a scene. Large texture size also limits the frame rate for a given memory bandwidth, especially when complicated filtering methods are used. These limits on the available textures and the frame rate constrain the quality of digital imaging in rendering a scene.
Texture compression (TC) techniques can effectively reduce the memory storage and memory bandwidth requirements in real-time rendering. For LDR textures, many compression schemes have been devised, including the de facto standard, DirectX® texture compression (DXTC), which may also be known as S3TC. DXTC has been widely supported by commodity graphics hardware.